Integrated mixing system for exhaust aftertreatment system

ABSTRACT

In one aspect, a swirl can mixer assembly for mixing a fluid with exhaust gas exhausted from an internal combustion engine is provided. The assembly includes an inlet portion including an injection area configured to receive a fluid injector for dispensing the fluid into the exhaust gas for mixing with the exhaust gas in the mixing assembly to produce an exhaust gas/fluid mixture, an outlet portion, and an extended mixing conduit fluidly coupled between the inlet portion and the outlet portion. The extended mixing conduit is curved about at least a portion of a circumference of the outlet portion to induce a swirl in the exhaust gas/fluid mixture such that the exhaust gas/fluid mixture enters the outlet portion tangentially thereto.

FIELD OF THE INVENTION

Exemplary embodiments of the invention relate to exhaust treatmentsystems for internal combustion engines and, more particularly, toexhaust treatment systems that fully mix fluids injected into an exhaustgas flow in a short physical length.

BACKGROUND

The exhaust gas emitted to an exhaust treatment system from an internalcombustion engine is a heterogeneous mixture that contains gaseousemissions such as carbon monoxide (“CO”), unburned hydrocarbons (“HC”)and oxides of nitrogen (“NO_(x)”) as well as condensed phase materials(liquids and solids) that constitute particulate matter. Catalystcompositions, typically disposed on catalyst supports or substrates, areprovided in various exhaust system devices to convert certain, or all ofthese exhaust constituents into non-regulated exhaust gas components.

An exhaust treatment technology in use for high levels of particulatematter reduction, particularly in diesel engines, is the ParticulateFilter (“PF”) device. There are several known filter structures used inPF devices that have displayed effectiveness in removing the particulatematter from the exhaust gas such as ceramic honeycomb wall flow filters,wound or packed fiber filters, open cell foams, sintered metal fibers,etc. Ceramic wall flow filters have experienced significant acceptancein automotive applications.

The filter in a PF device is a physical structure for removingparticulates from exhaust gas and, as a result, the accumulation offiltered particulates will have the effect of increasing the exhaustsystem backpressure experienced by the engine. To address backpressureincreases caused by the accumulation of exhaust gas particulates, the PFdevice is periodically cleaned, or regenerated. The regenerationoperation burns off the carbon and particulate matter collected in thefilter substrate and regenerates the PF device.

Regeneration of a PF device in vehicle applications is typicallyautomatic and is controlled by an engine or other controller based onsignals generated by engine and exhaust system sensors such astemperature sensors and back pressure sensors. The regeneration eventinvolves increasing the temperature of the PF device to levels that areoften above 600 C in order to burn the accumulated particulates.

One method of generating the temperatures required in the exhaust systemfor regeneration of the PF device is to deliver unburned HC (often inthe form of raw fuel) to an oxidation catalyst (“OC”) device disposedupstream of the PF device. The HC may be delivered by injecting fuel(either as a liquid or pre-vaporized) directly into the exhaust gasusing an HC injector/vaporizer. The HC is oxidized in the OC deviceresulting in an exothermic reaction that raises the temperature of theexhaust gas. The heated exhaust gas travels downstream to the PF deviceto thereby burn (oxidize) the particulate accumulation.

A challenge for designers, especially those involved in space limitedautomotive applications, is that injecting fluids such as HC into theexhaust gas upstream of an OC device, or any other device for thatmatter, must allow for sufficient residence time, turbulence anddistance in the exhaust flow for the injected fluid to becomesufficiently mixed with and vaporized in the exhaust gas prior toentering the device. Without proper preparation, the injected fluid willnot properly oxidize in the OC device and some unburned HC may passthrough the device. The result is wasted fuel passing through theexhaust treatment system and uneven temperatures within the devices.

A technology that has been developed to reduce the levels of NO_(x)emissions in lean-burn engines (ex. diesel engines) that burn fuel inexcess oxygen includes a Selective Catalytic Reduction (“SCR”) device.An SCR catalyst composition disposed in the SCR device preferablycontains a zeolite and one or more base metal components such as iron(“Fe”), cobalt (“Co”), copper (“Cu”) or vanadium (“V”) which can operateefficiently to reduce NO_(x) constituents in the exhaust gas in thepresence of a reductant such as ammonia (“NH₃”). The SCR catalyst may beapplied as a wash coat to either a conventional flow-through substrateor on the substrate of a particulate filter. The reductant is typicallydelivered as a liquid upstream of the SCR device, in a manner similar tothe HC discussed above, and travels downstream to the SCR device tointeract with the SCR catalyst composition; reducing the levels ofNO_(x) in the exhaust gas passing through the SCR device. Like the HCdiscussed above, without proper mixing and evaporation, the injectedreductant, urea or ammonia for instance, will not properly function inthe SCR device and some of the fluid may pass through the deviceresulting in wasted reductant as well as reduced NO_(x) conversionefficiency.

Typical exhaust treatment systems may include several exhaust treatmentdevices as described above. In many instances, whether historical ornot, the devices may comprise individual components that are seriallydisposed along an exhaust conduit that extends from the exhaust manifoldoutlet of the internal combustion engine to the tailpipe outlet of theexhaust treatment system. To meet more stringent exhaust emissionrequirements, the exhaust treatment devices may need to be lighted-offas quickly as possible in emission cycles. As such, it is desirable tolocate the exhaust treatment devices as close to the engine as possible,for example, close-coupled with turbochargers or exhaust manifolds. Asvehicle architectures become smaller and demand close-coupled positiondesigns, the desired length for an exhaust treatment system may notnecessarily be available.

Accordingly it is desirable to provide a system that will achieveuniform mixing and distribution of a fluid injected into the exhaust gasin an exhaust treatment system in a compact distance.

SUMMARY

In one aspect, a swirl can mixer assembly for mixing a fluid withexhaust gas exhausted from an internal combustion engine is provided.The assembly includes an inlet portion including an injection areaconfigured to receive a fluid injector for dispensing the fluid into theexhaust gas for mixing with the exhaust gas in the mixing assembly toproduce an exhaust gas/fluid mixture, an outlet portion, and an extendedmixing conduit fluidly coupled between the inlet portion and the outletportion. The extended mixing conduit is curved about at least a portionof a circumference of the outlet portion to induce a swirl in theexhaust gas/fluid mixture such that the exhaust gas/fluid mixture entersthe outlet portion tangentially thereto.

In another aspect, an exhaust gas treatment system configured to receiveexhaust gas from an internal combustion engine is provided. The systemincludes a catalyst device and a swirl can mixer assembly for mixing afluid with the exhaust gas. The swirl can mixer assembly includes aninlet portion including an injection area and a fluid injector coupledto the inlet portion and configured to dispense the fluid into theexhaust gas in the injection area for mixing with the exhaust gas in themixing assembly to produce an exhaust gas/fluid mixture. The assemblyfurther includes an outlet portion coupled to the catalyst device and anextended mixing conduit fluidly coupled between the inlet portion andthe outlet portion. The extended mixing conduit is curved about at leasta portion of a circumference of the outlet portion to induce a swirl inthe exhaust gas/fluid mixture such that the exhaust gas/fluid mixtureenters the outlet portion tangentially thereto.

The above features and advantages and other features and advantages ofthe invention are readily apparent from the following detaileddescription when taken in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects, features, advantages and details appear, by way ofexample only, in the following detailed description of embodiments, thedetailed description referring to the drawings in which:

FIG. 1 is a schematic view of an internal combustion engine andassociated exhaust treatment system embodying features of the invention;

FIG. 2 is a perspective view of a compact mixing assembly shown in FIG.1 and illustrating fluid flow therethrough;

FIG. 3 is a cross-sectional view of the compact mixing assembly shown inFIG. 2 and taken along line 3-3;

FIG. 4 is a perspective view of the compact mixing assembly shown inFIG. 1;

FIG. 5 is a cut-away view of the compact mixing assembly shown in FIG.4; and

FIG. 6 is a perspective view of an exemplary mixer device that may beused with the compact mixing assembly shown in FIGS. 1-5.

DESCRIPTION OF THE EMBODIMENTS

The following description is merely exemplary in nature and is notintended to limit the present disclosure, its application or uses. Itshould be understood that throughout the drawings correspondingreference numerals indicate like or corresponding parts and features.

Referring to FIG. 1, an internal combustion engine 10 is illustrated. Itshould be noted that the invention disclosed herein has application toany type of internal combustion engine requiring an exhaust treatmentsystem in which a fluid such as hydrocarbon (“HC”) or urea (or otherammonia (“NH3”) containing fluid or gas) is injected. In the descriptionbelow, a diesel engine 10 and associated exhaust treatment system 12 isdescribed. The diesel engine comprises a cylinder block 14 and acylinder head 16 which, when combined, define piston cylinders andcombustion chambers (not shown). Reciprocating pistons (not shown) aredisposed in the piston cylinders and are operable to compress air whichcombusts when compressed and mixed with an injected fuel in a mannerwell known in the art. Products of combustion, or exhaust gas 18, exitsthe cylinder head 16 through exhaust port 20 (which may be associatedwith an exhaust manifold (not shown)) that, in the exemplary embodimentshown, leads to the exhaust turbine side 22 of an exhaust driventurbocharger 24. The exhaust gas spins an impeller (not shown) which isrotatably mounted within the exhaust turbine side of the turbochargerand subsequently exits the turbocharger through an exit port 26. Theexit port is in fluid communication with the exhaust treatment system 12and exhaust gas 18 departing the turbocharger 24 through the exit port26 is transferred thereto.

The exhaust treatment system 12 may comprise one of many configurationsdepending upon the particular application of the engine 10 and itsinstallation (i.e. vehicle, stationary etc.). In the configuration shownin FIG. 1, exhaust gas 18 exiting the exhaust driven turbocharger 24enters an oxidation catalyst (“OC”) device 30 through an inlet cone 32that is in fluid communication with the exit port 26. The OC device 30may include, for example, a flow-through metal or ceramic monolithsubstrate (not shown) that is packaged in a stainless steel shell orcanister 36 having an inlet and an outlet in fluid communication withthe exhaust gas 18 in the exhaust treatment system 12. The substratetypically may include an oxidation catalyst compound disposed thereon.The oxidation catalyst compound may be applied as a wash coat and maycontain platinum group metals such as platinum (“Pt”), palladium (“Pd”),rhodium (“Rh”) or other suitable oxidizing catalysts, or combinationsthereof The OC device 30 is useful in treating unburned gaseous andnon-volatile HC and CO, which are oxidized to form carbon dioxide andwater.

In the exemplary embodiment, a compact mixing assembly or swirl canmixer assembly 40 is located immediately downstream of the OC device 30and is configured to receive exhaust gas exiting the OC device 30. Swirlcan mixer 40 includes in inlet portion 42, an outlet portion 44, and anextended mixing conduit 46 extending therebetween. In the illustratedexemplary embodiment, an outlet 48 of the OC device and an inlet 50 ofthe swirl can inlet portion 42 are configured with similar diameters tothereby provide a leak-free seal thereabout while imposing little or norestriction upon the flow of exhaust gas 18.

A reductant fluid injector 52 is mounted to swirl can mixer inletportion 42 upstream of the extended mixing conduit 46 and injects anammonia (“NH3”) based reductant 54 (e.g., FIGS. 2 and 3) into the flowof the exhaust gas 18 as it enters the extended mixing conduit 46. Theswirl can mixer 40 operates to vaporize the reductant 54 and to mix itwith the exhaust gas 18 in a manner that is described herein in moredetail.

The reductant 54 is mixed with the exhaust gas 18 in the swirl can mixer40 to form an exhaust gas/reductant mixture 56, and swirl can mixer 40induces a swirling action of mixture 56 that is tangential to or swirlsabout an axis 58 of the mixer outlet portion 44. The swirl inducedmixture 56 subsequently departs through a mixer outlet 60 and may betransported to a Selective Catalytic Reduction (“SCR”) device 62disposed below and in parallel alignment with the OC device 30.Similarly, the mixer outlet portion 44 is disposed below and in parallelalignment with the mixer inlet portion 42.

The SCR device 62 may include, for example, a flow-through metal orceramic monolith substrate that is packaged in a stainless steel shellor canister 64 having an inlet 66 and an outlet 68 in fluidcommunication with the exhaust gas/reductant mixture 56 in the swirl canmixer 40. An SCR catalyst composition disposed in the SCR device 62preferably contains a zeolite and one or more base metal components suchas iron (“Fe”), cobalt (“Co”), copper (“Cu”) or vanadium (“V”) which canoperate efficiently to reduce NO_(x) constituents in the exhaust gas 18in the presence of the ammonia (“NH3”) based reductant. The outlet 68 ofthe SCR device 62 may comprise an exhaust gas collector such as exitcone 70 having an outlet 72 configured with a flange member 74 thatallows the exhaust treatment system 12 to be fluidly connected to anexhaust gas conduit (not shown) that will conduct the exhaust gas toadditional exhaust treatment devices (if installed) and subsequently tothe atmosphere.

In the exemplary embodiment, the swirl can outlet portion 44 and the SCRinlet 66 are configured with similar diameters to thereby provide aleak-free seal thereabout while imposing little or no restriction uponthe flow of mixture 56. As illustrated in FIG. 2, canister 64 may alsoinclude a second OC device 76 and a particulate filter (“PF”) device 78.However, canister 64 may include only one of the SCR device 62, the OCdevice 76, and the PF device 78, or may include any combination thereof.The exhaust gas 18 may be mixed with a hydrocarbon (“HC”) (not shown)and oxidized in the second OC device 76 resulting in an exothermicreaction that raises the temperature of the exhaust gas. The heatedexhaust gas travels downstream to PF device 78 to thereby burn (oxidize)particulate accumulation in a known manner.

Referring to FIGS. 2-5, an exemplary swirl can mixer 40 is illustrated.The mixer 40 generally includes the inlet portion 42, the outlet portion44, and the extended mixing conduit 46 extending therebetween.

The mixer inlet portion 42 includes a rigid canister 80 having an axis82, and the canister 80 defines the inlet 50 and an outlet 84 of theinlet portion 42. The inlet 50 is oriented substantially perpendicularto the outlet 84, which is formed in an outer surface 86 of the canister80. The canister 80 includes an injection area 88 configured to receiveat least a portion of the reductant injector 52 for injection of thereductant 54 into the exhaust gas 18 upstream of the outlet 84.

The extended mixing conduit 46 generally includes an inlet 90, a mixingportion 92, a diffusing portion 94, and an outlet 96. As illustrated,mixing conduit 46 is curved and extends about a portion of thecircumference of the mixer outlet portion 44. This provides an extendedor lengthened path for mixing the exhaust gas 18 and the reductant 54 toincrease residence time therein for improved mixing.

The mixing portion 92 of conduit 46 includes a decreasing diameter orcross-sectional area between inlet 90 and the beginning of diffusingportion 94, which facilitates concentrating and accelerating the flow ofthe exhaust gas/reductant mixture 56 to promote increased mixingthereof. The mixing portion 92 may also include a mixer device 98positioned therein to facilitate further mixing between the exhaust gas18 and the reductant 56. As shown in FIG. 6, in the exemplaryembodiment, the mixer device 98 may include a plurality of radiallyextending blades 100 circumferentially spaced about a middle ring 102that defines an aperture 104. Blades 100 facilitate inducing a swirlmotion or vortex 105 (FIG. 3) in the gas mixture 56 to increase mixingof the exhaust gas 18 and the reductant 54. Further, middle ring 102acts as a venturi and diffuser by increasing the velocity of the mixture56 passing therethrough and diffusing the mixture 56 downstream thereofto facilitate improved mixing between the exhaust gas 18 and thereductant 54. Alternatively, any suitable mixer device may be used thatenables swirl can mixer 40 to function as described herein.

The diffusing portion 94 of conduit 46 includes an increasing diameteror cross-sectional area between the beginning of diffusing portion 94and the conduit outlet 96, which facilitates diffusing the exhaustgas/reductant mixture 56, thereby slowing the flow velocity of themixture 56 and increase mixing between the exhaust gas 18 and thereductant 54. Diffusing portion 94 includes an inner wall 99 at leastpartially defining the mixing conduit 46 to extend its overall lengthbetween the conduit inlet 90 and outlet 96. As shown in FIGS. 3 and 4,the curvature of the diffusing portion 94 extends the fluid path about aportion of the circumference of swirl can mixer outlet portion 44. Thisfacilitates both extending the length of the fluid path between mixerinlet and outlet portions 42, 44 as well as generating a larger scale,circumferential swirl 107 (FIG. 3) of the mixture 56 about outletportion axis 58.

The internal surface shape and the position and angle of the entry ofmixing conduit outlet 96 into the mixer outlet portion 44 determines theflow distribution into the downstream catalysts. For example, as shownin FIG. 5, a ratio of parameters may be a/D between approximately0.1˜0.40, b/D between approximately 0.15˜0.5, and c/D betweenapproximately 0.2˜0.6. However, these ratios can be altered to balancethe flow distribution and mixing for a desired overall performance.

The mixer outlet portion 44 includes a rigid canister 106 having axis58, and the canister 106 defines an inlet 108 and the outlet 60 of theoutlet portion 44. The inlet 108 is oriented substantially perpendicularto the outlet 60 and receives the mixture 56 from the outlet 96 withinduced swirl components 105, 107 from both the mixer device 98 and thecircumferential diffusing portion 94. The mixture 56 enters the mixeroutlet portion 44 tangentially thereto, and the rotation direction ofswirl components 105 and 107 are normal to each other, which break up inmultiple directions within the inner volume of swirl can mixer outletportion 44 to facilitate enhancing liquid reductant droplet vaporizationand mixing with the exhaust gas 18 prior to entering the SCR device 62.

In operation of the swirl can mixer assembly 40, exhaust gas 18 flowsinto mixer inlet portion 42 and reductant 54 is injected into theexhaust gas 18 by the injector 52. The exhaust gas/reductant mixture 56subsequently flows through outlet 84 to the extended mixing conduit 46.

The exhaust gas/reductant mixture 56 enters the extended mixing conduit46 through inlet 90. The exhaust gas 18 and reductant 54 continue to mixas the diameter or cross-section of the conduit mixing portion 92decreases, thereby increasing the velocity and mixing of the fluids 18,54. As the mixture 56 reaches the mixer device 98, a swirl 105 isinduced in a portion of the mixture 56 by blades 100 to enhance mixing,and a portion of the mixture 56 is subjected to a venturi effectproduced by the middle ring 102, thereby also increasing mixture betweenthe exhaust gas 18 and the reductant 54 across a wide range of exhaustflow rates.

The exhaust gas/reductant mixture 56 subsequently flows downstream ofthe mixer device 98 to the conduit diffusing portion 94, where thecurved, circumferential path of portion 94 induces the circumferentialswirl component 107 in the mixture that is tangential to swirl can mixeroutlet portion 44 and its axis 58. Further, the increasing diameter orcross-section of the diffusing portion 94 diffuses the mixture 56, whichreduces the flow velocity of mixture 56 and promotes further mixing ofthe exhaust gas 18 and the reductant 54 and also increases the residencetime of the mixture 56 in the outlet portion 94. The mixture 56, whichincludes swirl components 105, 107 produced by the mixer device 98 andthe circumferential diffusing portion 94, subsequently exits theextended mixing conduit 46 through outlet 96.

The exhaust gas/reductant mixture 56 enters the swirl can mixer outletportion 44 through inlet 108 from extended mixing conduit 46. The swirlcomponents 105, 107 of the fluid flow of mixture 56 break apart ordissipate within the canister 106, which enhances the mixing and liquiddroplet vaporization between the exhaust gas 18 and the reductant 54. Assuch, the exhaust gas 18 and the reductant 54 are sufficiently mixedprior to entering the SCR device 62, the second OC device 76, and/or thePF device 78 even though the exhaust treatment system 12 has a compactconfiguration. This is due in part to the extended length of the curvedmixing conduit 46 as well as the mixing and/or vaporization promoted bythe reducing diameter mixing portion 92, the swirl components 105, 107induced by the mixer device 98 and curved diffusing portion 94, theventuri/diffuser effect produced by the mixer device 98, the fluiddiffusion facilitated by expanding cross-section diffusing portion 94,and the fluid entering the mixer outlet portion 44 tangentially thereto.

While the invention has been described with reference to exemplaryembodiments, it will be understood by those skilled in the art thatvarious changes may be made and equivalents may be substituted forelements thereof without departing from the scope of the invention. Inaddition, many modifications may be made to adapt a particular situationor material to the teachings of the invention without departing from theessential scope thereof. Therefore, it is intended that the inventionnot be limited to the particular embodiments disclosed, but that theinvention will include all embodiments falling within the scope of thepresent application.

What is claimed is:
 1. A swirl can mixer assembly for mixing a fluidwith exhaust gas exhausted from an internal combustion engine, theassembly comprising: an inlet portion including an injection areaconfigured to receive a fluid injector for dispensing the fluid into theexhaust gas for mixing with the exhaust gas in the mixing assembly toproduce an exhaust gas/fluid mixture; an outlet portion; and an extendedmixing conduit fluidly coupled between the inlet portion and the outletportion, wherein the extended mixing conduit is curved about at least aportion of a circumference of the outlet portion to induce a swirl inthe exhaust gas/fluid mixture such that the exhaust gas/fluid mixtureenters the outlet portion tangentially thereto.
 2. The assembly of claim1, wherein the inlet portion is a canister having an inlet and an outletcoupled to the extended mixing conduit, wherein the outlet is locateddownstream of the injection area.
 3. The assembly of claim 2, whereinthe canister includes a cylindrical outer surface, wherein the inletportion outlet extends through the cylindrical outer surface.
 4. Theassembly of claim 1, wherein the outlet portion is a canister having aninlet coupled to the extended mixing conduit, and an outlet.
 5. Theassembly of claim 1, wherein the canister includes a cylindrical outersurface.
 6. The assembly of claim 1, wherein the extended mixing conduitincludes a mixing portion and a diffusing portion, wherein the mixingportion is coupled to the inlet portion and the diffusing portion iscoupled to the outlet portion, the mixing portion positioned upstream ofthe diffusing portion.
 7. The assembly of claim 6, wherein thecross-sectional area of the mixing portion decreases along a length ofthe mixing portion, the decreasing cross-sectional area configured tofacilitate increasing the velocity of the exhaust gas and the fluid tofacilitate mixing therebetween.
 8. The assembly of claim 6, wherein thecross-sectional area of the diffusing portion increases along a lengthof the diffusing portion, the increasing cross-sectional area configuredto facilitate diffusion of the exhaust gas and the fluid to improvemixing therebetween.
 9. The assembly of claim 6, further comprising amixer device located in the mixing portion of the extended mixingconduit, the mixer device configured to facilitate mixing of the exhaustgas and the fluid.
 10. The assembly of claim 9, wherein the mixer devicecomprises at least one of: a plurality of blades configured tofacilitate inducing a swirl in the exhaust gas/fluid mixture; and amiddle ring configured to facilitate producing a venturi effect on theexhaust gas/fluid mixture passing therethrough.
 11. An exhaust gastreatment system configured to receive exhaust gas from an internalcombustion engine, the system comprising: a catalyst device; and a swirlcan mixer assembly for mixing a fluid with the exhaust gas, the swirlcan mixer assembly comprising: an inlet portion including an injectionarea; a fluid injector coupled to the inlet portion and configured todispense the fluid into the exhaust gas in the injection area for mixingwith the exhaust gas in the mixing assembly to produce an exhaustgas/fluid mixture; an outlet portion coupled to the catalyst device; andan extended mixing conduit fluidly coupled between the inlet portion andthe outlet portion, wherein the extended mixing conduit is curved aboutat least a portion of a circumference of the outlet portion to induce aswirl in the exhaust gas/fluid mixture such that the exhaust gas/fluidmixture enters the outlet portion tangentially thereto.
 12. The systemof claim 11, wherein the fluid injector is a reductant injector and thefluid is a reductant.
 13. The system of claim 11, wherein the catalystdevice is at least one of a selective catalytic reduction (SCR) device,an oxidation catalyst (OC) device, and a particulate filter (PF) device.14. The system of claim 11, further comprising a second catalyst devicecoupled to the inlet portion.
 15. The system of claim 14, wherein thesecond catalyst device is an oxidation catalyst (OC) device.
 16. Thesystem of claim 11, wherein the extended mixing conduit includes amixing portion and a diffusing portion, wherein the mixing portion iscoupled to the inlet portion and the diffusing portion is coupled to theoutlet portion, the mixing portion positioned upstream of the diffusingportion.
 17. The system of claim 16, wherein the cross-sectional area ofthe mixing portion decreases along a length of the mixing portion, thedecreasing cross-sectional area configured to facilitate increasing thevelocity of the exhaust gas and the fluid to facilitate mixingtherebetween.
 18. The system of claim 16, wherein the cross-sectionalarea of the diffusing portion increases along a length of the diffusingportion, the increasing cross-sectional area configured to facilitatediffusion of the exhaust gas and the fluid to improve mixingtherebetween.
 19. The system of claim 16, further comprising a mixerdevice located in the mixing portion of the extended mixing conduit, themixer device configured to facilitate mixing of the exhaust gas and thefluid.
 20. The assembly of claim 19, wherein the mixer device comprisesat least one of: a plurality of blades configured to facilitate inducinga swirl in the exhaust gas/fluid mixture; and a middle ring configuredto facilitate producing a venturi effect on the exhaust gas/fluidmixture passing therethrough.